Hi I am stumped on an ap bio homework question:
In the cyclic reaction sequence called the krebs cycle, which chemical event does not take place?
a.The acetyl group is joined with a four carbon molecule, oxaloacetate.
b. Two carbons per cycle are made into CO2 molecules.
c. Electrons generated are used to produce NADH.
d. Pyruvate molecules are restored to the cycle.
e. The resulting six carbon molecule is oxidized.
I am leaning towards a, but I am not really sure.
Any help would be greatly appreciated!
To determine which chemical event does not take place in the Krebs cycle, let's analyze each option:
a. The acetyl group is joined with a four carbon molecule, oxaloacetate: This is an accurate description of one step in the Krebs cycle, where the acetyl group from acetyl-CoA combines with oxaloacetate to form citrate. This step does occur in the cycle.
b. Two carbons per cycle are made into CO2 molecules: This statement is true. In each cycle of the Krebs cycle, two carbons are released in the form of carbon dioxide (CO2).
c. Electrons generated are used to produce NADH: This statement is also accurate. During the Krebs cycle, electrons generated from various reactions are used to produce NADH, which is an energy-rich molecule.
d. Pyruvate molecules are restored to the cycle: This statement is incorrect. The Krebs cycle does not involve pyruvate molecules. Pyruvate molecules are produced during the process of glycolysis, which occurs prior to the Krebs cycle.
e. The resulting six carbon molecule is oxidized: This statement is true. The six-carbon molecule, citrate, is gradually oxidized during the Krebs cycle, releasing energy in the form of NADH and FADH2.
Based on the analysis, option d is the correct answer. The restoration of pyruvate molecules to the cycle does not occur in the Krebs cycle.